‘Super-terrestrial’ exoplanet discovered orbiting one of the oldest stars in the Milky Way

Scientists have located a “Super Earth” believed to orbit one of the oldest stars in the Milky Way galaxy. The exoplanet derives its title because it is believed to be about three times the mass of Earth, with a size 50% larger than our home planet.

The planet, known as TOI-561b, has been described in a new study accepted for publication in The Astronomical Journal. Despite the mass of the planet, its density is about the same as that of the Earth, astronomers found in the study.

“We report the discovery of TOI-561, a multi-planetary system in the thick galactic disk that contains a rocky ultra-short period (USP) planet,” the study said.

The planet takes its name from NASA’s 2018 Transiting Exoplanet Survey Satellite (TESS) planet-hunting mission. The “YOU” in TOI-561b stands for TESS Object of Interest. It is located outside the solar system, in the thick galactic disk of the Milky Way, explains a CNN report. Due to its proximity to the host star, it only takes less than half an Earth day to complete an orbit around it.

“For every day that you are on Earth, this planet revolves around its star twice,” Stephen Kane, study co-author and astrophysicist at the University of California at Riverside, said in a statement. Researchers determined the mass, radius and density of the planet using the WM Keck Observatory in Hawaii.

(Representative image: Reuters)

This close proximity to “super-Earth” results in an average planet surface temperature of over 2,000 Kelvin, or 3,140 degrees Fahrenheit. TOI-561b is therefore too hot to be habitable. Although since astronomers know that the rocky planet and its star form a 10 billion year old system, they wonder if the planet was home to life at any point in its past.

“TOI-561b is one of the oldest rocky planets ever to be discovered,” study lead author Lauren Weiss said in a statement. “Its existence shows that the universe has formed rocky planets almost since its inception 14 billion years ago.” In comparison, our sun is only 4.5 billion years old.

These older planets turn out to be less dense than the more recently formed planets. This is because there weren’t as many heavy elements present in the universe at the time. Such elements were ultimately created by stars who met their end in a supernova.

The study highlights two other planets orbiting the star, which are both likely gaseous and larger than TOI-561b.

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